Electron multiplier amplifier discharge device



July 9, 1968 R. F. FRANKLIN ELECTRON MULTIPLIER AMPLIFIER DISCHARGEDEVICE 2 Sheets-Sheet 1 Filed Aug.

' 3,392,296 ELECTRON MULTIPLIER AMPLIFIER I DISCHARGE DEVICE Robert F.Franklin, Chatham, N.J., assignor to Wagner Electric Corporation, acorporation of Delaware Filed Aug. 27, 1965, Ser. No. 483,118 12 Claims.(Cl. 313-44) This invention relates to an electron discharge devicecontaining a plurality of dynodes in addition to the usual anode,cathode and control electrodes. The invention has particular referenceto a discharge device which contains a plurality of cooling fins, atleast one for each dynode, for cooling the electrodes within thedischarge envelope and for forming a part of the envelope wall.

The electron discharge device described herein includes a centralcathode, one or more control electrodes, a plurality'of louvereddynodes, and an anode, all grouped in spaced relation about a commonaxis. This form of multiplier amplifier is old in the art and has beendescribed in books and other publications. The present inventioncomprises an improvement on prior art designs wherein a plurality ofcooling fins extend above and below the discharge space, these fins eachincluding a pair of adjoining cylindrical members which are joined ornear their extremities afterthe discharge components have beenpositioned. This design not only provides excellent cooling of thedischarge components but also permits much easier assembly. The fins mayalso be used to make contact with a socket for connection to an externalcircuit.

Throughoutthe specification and claims, the term dynode denotes a seriesof intermediate electrodes, generally spaced between a cathode and ananode, and given a potential more positive than the cathode. Theelectrons from the cathode strike an adjacent dynode and generatesecondary electrons which are passed on to other dynodes.

One of the objects of this invention is to provide an improved electrondischarge device whichavoids one or more of the disadvantages andlimitations of prior art devices.

Another object of the invention is to reduce the assembly time of adischarge device having a plurality of concentric components. 7

Another object of the invention is to increase the accuracy of theplacement of component parts in an electron discharge device.

Another object of the invention is to increase the dis sipation of heatgenerated by the components in a multiple component dis-charge device.

Another object of the invention is to provide a large contact area foreach of the discharge device components so that connection can be easilymade to anexternal circuit.

Theinventioncomprises an electron discharge device having a sealedenvelope containing a cathode for the emission of electrons and an anodefor collecting emitted electrons. A plurality of cylindrical secondaryemission dynodes are mounted between the anode and cathode and in axialalignment with them. Each dynode is formed with angular louveredportions which are disposed in slots formed in the dynode sheet. Eachdynode and the anode are secured to a plurality of insulator rings forholding the discharge components in position. Each of the components isalso connected to a metal cooling fin which extends beyond the interiorenvelope space.

One of the features of the invention includes the formation of eachcooling fin by combining two adjacent metal cylinders which are weldedtogether at their extremities.

Another feature of the invention includes the use of United StatesPatent ice insulator rings made of ceramic material and metalized by thedeposition of a molybdenum alloy on two of its sides. The components andcooling fins are brazed to this metalized film.

Another feature of the invention includes a louvered anode and a soliddynode positioned on the outside of the anode.

For a better understanding of the present invention, together with otherand further objects thereof, reference is made to the followingdescription taken in connection with the accompanying drawings.

FIG. 1 is a perspective view of the discharge device with a portion cutaway to show the internal structure;

FIG. 2 is a top view of the discharge device;

FIG. 3 is a partial cross sectional view, to an enlarged scale, showingone of the dynodes and a cooling fin prior to welding its upper edge;

FIG. 4 is a cross sectional view of the discharge device shown in FIG. 1and is taken along a horizontal plane which bisects the device. Thisview shows the internal structure of the device and the angulardisposition of the louvers; and

FIG. 5 is a schematic diagram of connections showing how the dischargedevice may be connected as a high-gain amplifier. In this diagram threecontrol electrodes are employed and the device is connected for positivepulse amplification.

Referring now to the drawings, the discharge device 10 includes an outerenvelope shell 11, a cathode 12, and a plurality of ceramic insulatorrings 13 which generally form an upper and lower wall defining thedischarge space within the envelope. Between each of the adjacent rings13 is a cooling fin 14, formed by two metal sheets which may be closefitting over their entire extent. As shown in FIG. 3, the base of onesheet 14-1 includes a turned-over portion 15 which is in contact withthe lower face of an insulator ring 13. The base of the adjoining sheet14-2 includes a turned-over portion 16 which is joined to the lower faceof the adjacent ring. The turned-over portion 16 supports a metal ring17 and a dynode 18 which is formed with louvers 20. The lower ends ofthe dynodes 18 are secured in a similar manner to turned-over portionsof the lower cooling fins 21 and to metal rings 22, similar inconstruction to the upper rings 17.

While it is convenient to weld the upper and lower extremities of sheets14, it is obvious that a metal weld may be made at an intermediateposition such as indicated by arrow 23. Such a weld may be made by twocompression rollers mounted on arms (not shown) which may extend intothe spaces between the cooling fins. The invention does not depend upona Weld or soldered joint at the extreme upper and lower ends of thecooling fins.

The cathode 12 is shown mounted in the axial position of the device. Theconstruction, above described, may be used as a diode, and in such acase there will be no control grids surrounding the cathode. FIG. 1shows an inner grid 23 and an outer grid 24 which may be used in variouscircuits for the control of amplifier output currents. Other controlelectrodes may be added. The invention does not depend upon the numberof control elements used.

When this discharge device is first assembled and all the componentshave been secured in. place, the device may be exhausted by connecting avacuum pump to an exhaust tube 25 which is sealed into the centralportion of the upper central ceramic disk. After the exhaust processesand the final pumping cycle, the exhaust tube 25 is pinched off making apinched seal 26. This seal is then protected by a hollow cylindrical cap27 which may be attached to the central structure by a plurality ofscrews 28.

The composite upper disk formed by rings 13 and the lower disk formed bysimilar ceramic rings is secured to the outer portion of the envelope 11by an upper bracket 30 and a lower bracket 31. These brackets aresecured to the outer envelope wall 11 at the edges 30A and 31A. Thebrackets 30 and 31 are brazed to the rings by the use of the usualmetallic film deposited upon the ceramic rings 13. These two bracketsare for assembly convenience only and any other type of fastener meansmay be used.

The cross sectional view shown in FIG. 4 illustrates one preferred formof the invention. The cathode 12 and the two control electrodes 23 and24 are shown in abbreviated form because they form no part of theimprovements which constitute the invention. The first, second, thirdand fourth dynodes 18 are formed with louvers 20 which have been punchedfrom the dynode sheet and bent into an angle which is substantially 45degrees from the tangent of the dynode sheet at that point. It should benoted that the louvers 20 are staggered, that is, the louver extensions20 extend clockwise in the first dynode and counter-clockwise in thesecond dynode. This design helps to increase the generation of secondaryelectrons but any other type of louver or louver angle may be used.

The anode 32 in this design is positioned between the last two dynodesand it contains a plurality of louvered portions 32 which are bent sothat they make an angle of substantially 90 degrees with the tangent ofthe anode sheet. The last dynode 33 is solid, having no slots norperforations, and, as shown, is on the outside of anode 32. It has beenfound that this arrangement of electrodes produces more load current anda greater amplifier gain than if the anode were solid and positioned onthe outside of all the dynodes.

The diagram of connections shown in FIG. is one example of the circuitwhich may be used with this device. The cathode 12 employes an internalheater 34 and there are three control electrodes 23 and 24. The mainpower supply 35 is a 1,900 volt direct current supply and is bridgedacross six neon discharge tubes 36, each arranged for the voltage shownin the figure. Resistors may be used instead of the neon diodes. Thedischarge tubes 36 may be replaced by Zener diodes or any other type ofvoltage regulating means may be used. An additional power supply 37 isconnected between the anode 32 and the outside dynode 33. This dynodealso generates secondary electrons, some of which are collected by theanode. The load 38 is connected in series with the anode 32 and thedirect current supply 35.

The first control electrode 23 is biased by a battery 40 to volts belowthe cathode potential and is connected in series with a resistor 41which in this case is 40,000 ohms. Input terminals 42 are connected tothe cathode 12 and the first control electrode 23 in series with ablocking capacitor 43. When a short positive pulse of volts is appliedto input terminals 42, an anode current of 5 amperes flows through the250 ohm load resistor 38.

Insulator rings 13 may be made of any suitable material but it has beenfound that a ceramic composed of powdered aluminum oxide, when pressedand sintered, forms the best insulating material. These rings are thencovered with a slurry of powdered molybdenum and manganese mixed withamyl acetate and powdered cellulose. After drying and heating in ahydrogen furnace at about 1,500 C. for ten minutes, the metal film isplated with either nickel or gold. This film forms a substantial basefor brazing with any type of metal electrode.

It should be noted that the extremities of fins 14 may be joined by anywell-known process, such as welding, soldering or brazing.

The foregoing disclosure and drawings are merely illustrative of theprinciples of this invention and are not to be interpreted in a limitingsense. The only limitations are to be determined from the scope of theappended claims.

I claim:

1. An electron discharge device comprising, a sealed envelope containinga cathode for the emission of electrons and an anode for collectingemitted electrons, a plurality of cylindrical secondary emission dynodesmade of conductive sheet and mounted in axial alignment with thecathode, said dynodes including angular louvered portions disposedadjoining slots formed in the dynode sheet for the generation ofsecondary electrons when bombarded by other electrons under theinfluence of an electric field, a plurality of insulator rings securedtothe ends of said dynodes for holding the dynodes in position, and aplurality of metal cooling fins secured to said insulator rings and tothe ends of the dynodes, said fins forming spacers between the insulatorrings and extending away from the interior envelope space.

2. An electron discharge device comprising, a sealed envelope containinga cylindrical cathode for the emission of electrons and an anode forcollecting emitted electrons, a plurality of cylindrical secondaryemission dynodes made of conductive sheet and mounted in axial alignmentwith the cathode, said dynodes including angular louvered portionsdisposed adjoining slots formed in the dynode sheet for the generationof secondary electrons when bombarded by other electrons under theinfluence of an electric field, a plurality of insulator rings securedto the ends of said dynodes for holding the dynodes in position, and aplurality of metal cooling fins secured to said insulator rings and tothe ends of the dynodes, said fins forming spacers between the insulatorrings, each of said fins including a pair of cylindrical sheets joinedat their outer extremeties and forming a part of the envelope.

3. An electron discharge device as claimed in claim 2 wherein saidenvelope also includes a control electrode mounted adjacent to thecathode surface for altering the electric field adjoining the cathode.

4. An electron discharge device 'as claimed in claim 2 wherein saidenvelope also includes a cylindrical anode sheet and a cooling finjoined to the anode edge.

5. An electron discharge device as claimed in claim 4 wherein said anodeis formed. with louvered portions disposed adjoining slots formed in theanode sheet.

6. An electron discharge device as claimed in claim 5 wherein said anodelouvered portions are disposed at substantially right angles to theanode sheet and wherein said slots are formed parallel to thecylindrical axis.

7. An electron discharge device comprising, a sealed envelope containinga cathode for the emission of electrons and a cylindrical anode forcollecting emitted electrons, a plurality of cylindrical secondaryemission dynodes mounted in axial alignment with the cathode and theanode, said dynodes including angular louvered portions disposedadjoining slots formed in the dynodes for the generation of secondaryelectrons, said dynodes positioned between the cathode and anode inspaced relation, a plurality of insulator rings secured to the ends ofsaid dynodes and said anode for holding the dynodes and anode inposition, a plurality of metal cooling fins respectively secured to eachinsulator ring and to the ends of each dynode and anode, said fins eachincluding a pair of adjoining cylindrical sheets joined adjacent totheir outer extremities and forming a part of the envelope.

8. An electron discharge device as claimed in claim 7 wherein saidinsulator rings are made of ceramic and are metalized on two sides priorto assembly by the deposition of a molybdenum alloy.

9. An electron discharge device as claimed in claim 7 wherein saidinsulator rings and said cooling fins are secured respectively to bothends of the dynodes and the anode.

10. An electron discharge device as claimed in claim 5 7 wherein saiddynodes are secured to said insulator rings by brazing to a metalizedsurface film on the rings. 11. An electron discharge device as claimedin claim 7 wherein an additional solid dyno'de is positioned around theanode on the anode side away from the 5 cathode and wherein said anodeis formed with louvered portions adjoining slots in the anode.

12. An electron discharge device as claimed in claim 7 wherein the outeredges of said cooling fins are joined by welding.

References Cited UNITED STATES PATENTS 1,683,134 9/1928 Hull 313-105 X2,189,318 2/ 1940 Krenzien 313-105 2,246,172 6/ 1941 Hergenrother313-105 JOHN W. HUCKERT, Primary Examiner.

10 R. F. POLISSACK, Assistant Examiner.

1. AN ELECTRON DISCHARGE DEVICE COMPRISING, A SEALED ENVELOPE CONTAININGA CATHODE FOR THE EMISSION OF ELECTRONS AND AN ANODE FOR COLLECTINGEMITTED ELECTRONS, A PLURALITY OF CYLINDRICAL SECONDARY EMISSION DYNODESMADE OF CONDUCTIVE SHEET AND MOUNTED IN AXIAL ALIGNMENT WITH THECATHODE, SAID DYNODES INCLUDING ANGULAR LOUVERED PORTIONS DISPOSEDADJOINING SLOTS FORMED IN THE DYNODE SHEET FOR THE GENERATION OFSECONDARY ELECTRONS WHEN BOMBARDED BY OTHER ELECTRONS UNDER THEINFLUENCE OF AN ELECTRIC FIELD, A PLURALITY OF INSULATOR RINGS SECUREDTO THE ENDS OF SAID DYNODES FOR HOLDING THE DYNODES IN POSITION,